The present invention relates to an apparatus and method for withdrawing a continuously advancing yarn with a suction device which removes the yarn in an air stream. More particularly, the present invention relates to an apparatus and method for threading up a freshly spun synthetic filament yarn onto fast moving machine parts, and as the yarn continuously advances from a spinneret.
The design and construction of yarn suction devices, such as the so called suction guns, have been a source of difficulty, since they are unable to provide adequately high yarn tensions where the yarn speeds are greater than about 4,000 meters per minute (65-70 meters per second). Such suction guns generally serve the purpose of withdrawing a continuously advancing yarn, particularly synthetic filament yarn, when the spinning operation is interrupted, for example, in order to doff packages, and the withdrawn yarn is diverted to a waste container. In such suction guns, the yarn is subjected to a strong air current. However, the applicability of such devices is limited to yarn speeds of about 4,000 meters per minute, since at these high speeds, the present suction devices are not able to provide the required yarn tension in order to thread up the yarn on the feed godet or take-up device of the spinning machine. With inadequate tension, it is likely that the yarn will form a lap on the godet or take-up device. In addition, the compressors or vaccuum pumps which are required at these high yarn speeds, become a significant cost factor by reason of their large power requirement, even though these devices are needed only temporarily when the operations are interrupted. Further, the efficiency of the known suction guns and air injectors is so low that their use becomes uneconomical at high yarn speeds.
To overcome the limitations of the known yarn suction devices as outlined above, it has been suggested that the suction current be generated by a liquid, such as water, and with pressures of about 80 bar and above. However, this method has not proven to be successful, since the requirement of removing the required quantities of water without undue expense has presented a difficult problem. In addition, hydraulic problems developed, since even a pressure of 51 bar is necessary for a frictionless flow of fluid in order to obtain a velocity flow of about 6,000 meters per minute (100 meters per second). Further, it is necessary that the yarn be first advanced by an air suction current, and then by a fluid current, which further complicates the design.
It is accordingly an object of the present invention to provide a yarn withdrawal apparatus and method which overcomes the above noted limitations of the prior systems, and which is adapted to withdraw a yarn at high speed and relatively high yarn tension, and so as to facilitate its thread-up onto the rapidly moving components of the spinning machine.